PROJECT SUMMARY To maintain skeletal muscle homeostasis and to repair damaged muscle, a functional pool of muscle stem cell (MuSC) undergoes asymmetric division in which committed progenies proliferate, differentiate, and fuse with existing myofibers or form de novo myofibers, while other populations of MuSC progeny self-renew to replenish the quiescent stem cell pool for future rounds of regeneration. Due to these unique properties, MuSC has been an attractive target for interventions, and cell-based therapy has been extensively studied to treat a variety of muscle wasting conditions. While direct transplantation of MuSC contributes to muscle regeneration to some degree, the clinical efficacy of direct cell transplantation is severely limited by sub-optimal engraftment, survival, and lack of functional benefits. To overcome these challenges, we engineered polyethylene glycol (PEG)- Maleimide hydrogels functionalized with adhesion ligands found in the native MuSC niche. Excitingly, our preliminary data show that MuSC delivered via biomimetic vehicle exhibit a significant improvement in transplantation efficiency compared to cells only control. To build upon our exciting preliminary findings, this proposal will test the working hypothesis that MuSC delivered within PEG-mal hydrogel functionalized to mimic native niche will synergistically augment long-term stem cell engraftment, restore regenerative, metabolic, and contractile function of dystrophic recipient muscle. As such, following specific aims will be investigated: Aim1 is to evaluate engineered PEG-mal hydrogel for optimal delivery, survival, engraftment, and MuSC function in vivo. Aim 2 examines whether co-delivery of MuSC and selected stem cell niche factors, VEGF and GDNF delivered within the biofunctional hydrogel, synergistically boost transplant efficiency and muscle function. The outcomes of this work serve as a vehicle for translating the basic sciences to the clinics, where the engineered biomaterial will contribute to accelerating the repair for the muscle traumatic injury, as well as other degenerative muscle diseases in human patients.